Silver enhancement

Goode NP, Shires M, Crellin DM, et al. Post-embedding double-labeling of antigen-retrieved ultrathin sections using a silver enhancement-controlled sequential immunogold (SECSI) technique. J. Histochem. Cytochem. 2004 52 141-144. 

Bronckers, A.J.J., Gay, S., Finkelman, R.D., and Butler, W.T. (1987) Immunolocalization of Gla proteins (osteocalcin) in rat tooth germs Comparison between indirect immunofluorescence, peroxidase-antiperoxidase, avidin-biotin-peroxidase complex, and avidin-biotin-gold complex with silver enhancement./. Histochem. Cytochem. 35, 825-830. 

X.D. Su, S.F.Y. Li, and J. O Shea, Au nanoparticle- and silver-enhancement reaction-amplified micro-gravimetric biosensor. Chem. Commun. 8, 755-756 (2001). 

J. Wang, R. Polsky, and X. Danke, Silver-enhanced colloidal gold electrochemical stripping detection of DNA hybridization. Langmuir 17, 5739-5741 (2001). 

H. Cai, Y. Wang, P. He, and Y. Fang, Electrochemical detection of DNA hybridization based on silver-enhanced gold nanoparticle label. Anal. Chim. Acta 469, 165-172 (2002). 

X. Chu, X. Fu, K. Chen, G. Shen, and R. Yu, An electrochemical stripping metalloimmunoassay based on silver-enhanced gold nanoparticle label. Biosens. Bioelectron. 20, 1805-1812 (2005). 

Gold particle conjugated swine anti rabbitt IgG, after silver enhancement. 

Fig. 1. Schematic drawing of various immune methods for localization of antigens. (A) Direct method. (B) Indirect method. (C) Immunogold with silver enhancement. (D) Peroxidase-antiperoxidase method. (E) Avidin-biotin system.

Immunolabel sections (in the case of Sawada and Esaki, nanogold was conjugated to the secondary antibodies and silver enhancement was employed [34].)... 

Yamashita S. Intranuclear localization of hormone-occupied and -unoccupied estrogen receptors in the mouse uterus application 1 nm immunogold-silver enhancement procedure to ultrathin frozen sections. JElectron Microsc 1995 44 22-29. 

Sawada H, Esaki M. Use of nanogold followed by silver enhancement and gold toning for postembedding immunolocalization in osmium-fixed, Epon-embedded tissues. J Electron Microsc 1994 43 361-366. 

Colloidal gold. This is a useful label for both direct and indirect staining methods since it requires no further reagent additions. Gold probes may be readily seen by light microscopy when coupled with silver enhancement and in addition, being electron dense, offer excellent sensitivity for the electron microscope. 

Other labels that have particular uses for electron microscopy are ferritin (11) and colloidal gold particles (12,13) (see Chapters 40-45). Gold particles are available in different sizes, therefore allowing simultaneous detection of several components on the same sample. Colloidal gold may also be detected with the light microscope following silver enhancement (see Chapter 29). In addition, radioactive labels have found some use in both light and electron... 

Fig. 1. Small intestine formaldehyde-fixed, paraffin-embedded. Section was stained with Concanavilin A conjngated to 5-nm colloidal gold. The gold was then silver-enhanced. Staining of mucous on the cell snrface and in goblet cells is seen.

A) Bright-field microscopy. The silver-enhanced gold appears as a dark stain. 

Silver-enhancing solution (II) 60 mL protective colloid (25% gum arabic or 50% PEG [20,000 mol wt] or PVP), 10 mL 2 M citric acid or sodium citrate, and 850 mg hydroquinone dissolved in 15 mL deionized glass-distilled water mix thoroughly adjust pH to 3.8 immediately before use, add 110 mg silver lactate dissolved in 15 mL deionized glass-distilled water (see Note 2). 

Immunogold staining can be used successfully at the light microscopic level if the gold is silver-enhanced. Enhancing soluhons may be made up in the laboratory, but because of their instability and light sensitivity, the commercially available silver-enhancing kits are preferable. 

Prepare silver-enhancing solution immediately prior to use, and cover the sections with the solution (see Note 6). 

After fixation and labeling, silver-enhance the gold using a commercially available kit. Generally, the time needed for enhancement for SEM is around 5 min. Dehydrate the samples, and critically point-dry. 

The silver-enhanced gold can be detected in the scanning electron microscope using backscattered electron imagining. 

Goode, D. and Mangel, T. K. (1987) Backscattered electron imaging of immuno-gold labeled and silver-enhanced microtubules in cultured mammalian cells. 

Scopsi, L. (1989) Silver-enhanced colloidal gold method, in Colloidal Gold, vol. 1 (Hayat, M. A., ed.), Academic, New York, pp. 251-295. 

Burry, R. W., Vandre, D. D., and Hayes, D. M. (1992) Silver enhancement of gold antibody probes in pre-embedding electron microscopic immunocytochemistry. J. Histochem. Cytochem. 40, 1849-1856. 

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